There are a great many ways of shaping, folding and welding together plastic-film-coated paper material in order to produce packagings for liquid foodstuffs such as milk, juices and the like.
A commercially common method of producing a foodstuff packaging and filling it with a liquid foodstuff is shown in principle in FIG. 1. A paper web 1 is shaped continuously into a tube by the two longitudinal edges 1a–b of the paper web being welded together, and the foodstuff in question is then filled into the newly formed tube. In the next process step, the tube is divided into packagings by being transversely sealed and cut along the transverse seal so that pillow-shaped packaging blanks are formed, which are given their final shape by the corners being folded in and fastened to the side surfaces of the packaging. A commercially well-known example of a packaging which is shaped in this way is the cuboid Tetra Brik (registered trademark) packaging produced by Tetra Pak.
The packaging material comprises at least one layer of paper and at least one layer of plastic. The plastic layer provides the paper layer with the necessary resistance to wet and is moreover intended to be partly melted in order to weld different portions of the packaging material together.
Recently, this type of packaging has been provided with various types of opening arrangement.
For example, U.S. Pat. No. 4,725,213 discloses an opening arrangement made of plastic which has been injection-moulded directly in place on a packaging material. A pair of mould halves is moved into engagement around a punched-out hole in the packaging material, and a heated thermoplastic material is injected into the mould cavity and thus forms an opening arrangement which covers the hole punched in the packaging material. The mould halves are shaped so that the injection-moulded opening arrangement comprises two flanges which extend around the periphery of the hole and lie against opposite sides of the packaging material around the edge of the punched-out hole, the opening arrangement gripping around the edge of the hole and in this way sealing against the packaging material.
U.S. Pat. No. 6,454,161 discloses another variant of such an opening arrangement. This opening arrangement has moreover been provided with tamper evidence which indicates to the consumer whether or not the packaging has been opened previously. In the design disclosed, however, problems may arise in some cases in connection with distribution because the opening arrangement disclosed extends up from the top side of the packaging. When a number of packagings are stacked on top of one another, there is a risk that the tamper evidence will be compressed and damaged, so that it is no longer unbroken even though the packaging has not been opened. If, to solve this problem, attempts are made to make the tamper evidence stronger, however, the problem arises that it is difficult for the consumer to open the packaging the first time when the tamper evidence has to be broken.
A further problem which should be mentioned in the context is that some configurations of opening arrangement suffer from the problem that the fastening surface to which the tamper evidence is fastened tends to come loose if it is subjected to great loads during distribution or when a consumer intends to open the packaging for the first time.